Field of the Invention
The present invention relates to a plasma processing method, a storage medium, and a plasma processing apparatus, and in particular relates to a plasma processing method that carries out etching processing on a high-dielectric-constant insulating film formed on a substrate.
Description of the Related Art
As semiconductor devices manufactured from semiconductor wafers as substrates are made smaller in size and with an increased degree of integration, there are increased demands to make gate insulating films of transistors and dielectric portions of capacitors (i.e. insulating films) of the semiconductor devices thinner. An insulating film satisfying these demands for thinness is only a few atoms thick, and in this case, with the conventional insulating film material SiO2, current leakage through the insulating film due to a quantum tunneling effect increases. It is thus difficult to use SiO2 as the material of such a thin insulating film.
In response to this problem, high-dielectric-constant insulating film materials according to which there is no current leakage even if a large current is passed have been developed. Such high-dielectric-constant insulating film materials are metal-based materials; specifically, an oxide of hafnium (Hf) or zirconium (Zr), or such an oxide with silicon (Si) additionally contained therein, or an oxide of aluminum (Al), or the like, can be used. However, there is a problem with these high-dielectric-constant insulating film materials that, in the case that etching is carried out using a plasma of a fluorine gas-based mixed gas as conventionally used in the etching of SiO2, the etching rate is slow.
A metal-based insulating film can be etched with a high etching rate using chemical etching comprised of a combination of corrosion with a corrosive gas and high temperature processing, but there are many problems, for example to carry out such chemical etching, a corrosion processing chamber and a high temperature processing chamber are both required, and hence a new system construction is required, and the cost of the system increases.
In recent years, there has thus been developed a plasma processing method in which a high-dielectric-constant gate insulating film is etched using a conventional etching apparatus with a plasma of a mixed gas comprised of argon (Ar), helium (He), or a mixed gas of argon and helium, with methane (CH4) added thereto (a noble gas-based mixed gas) (see Japanese Laid-open Patent Publication (Kokai) No. 2005-39015).
However, with a low sputter etching apparatus, even if a plasma of such a noble gas-based mixed gas is used, the etching rate is still slow, i.e. the required etching rate cannot be realized. Moreover, with a high sputter etching apparatus, the etching rate is sufficiently high, and hence the required etching rate can be realized, but silicon nitride (SiN), which is the material of a hard mask, is also etched with a high etching rate, and hence it is difficult to secure a good (high) etching selectivity ratio for the high-dielectric-constant insulating film versus the hard mask. That is, there is a problem that the etching controllability for the high-dielectric-constant insulating film is still low.